1. Field of the Invention
The present invention relates to a plasma processing method and a plasma processing apparatus for plasma processing a layer to be etched by using a resist film.
2. Description of the Related Art
In a mask process for forming a desired pattern during a semiconductor manufacturing process, patterning is performed on a layer to be etched via exposure and development after coating a photosensitive film on the layer to be etched. Here, in order to prevent reflection during the exposure, an anti reflection coating film (hereinafter, also referred to as an ARC film) is formed between the layer to be etched and the photosensitive film. For example, Patent Reference 1 discloses an etching method having a high etching rate and capable of etching with high etching selectivity when etching an ArF resist film to a desired pattern while suppressing reflection by using an anti reflection coating film on a layer to be etched (an organic film, a silicon oxynitride film (hereinafter, referred to as an SiON film)).
However, during an etching process using an ArF resist film as a mask, since plasma resistance of the ArF resist film is low, a reduction amount of the resist film is high, and thus a residual film of the resist film is low. Also, a line width of a pattern is not uniform, and thus line width roughness (hereinafter, referred to as LWR) deteriorates as the pattern is deformed.
Accordingly, Patent Reference 2 discloses a method of increasing etch resistance of a resist film by plasmatizing a gas including an H2 gas and performing plasma process (hardening process) of the resist film to inject H+ ions into the resist film, before a process of etching an anti reflection coating film by using an ArF resist film as a mask.
However, when an H2 gas is used during a hardening step, residues are generated as silicon is deposited in an open area (a large hole or the like) inside a processing container, thereby adversely affecting an etching process afterward.
3. Prior Art Reference                (Patent Reference 1) Japanese Patent Laid-Open Publication No. 2007-180358        (Patent Reference 2) Japanese Patent Laid-Open Publication No. 2004-163451        